The present invention relates to an elevator system driven by a linear motor in which a cage and a counter weight are alternatingly elevated up and down by means of a hoisting rope in a hoistway of a multistoried building, for example, with excellent elevating performance during the elevating motion of the linear motor elevator system.
A conventional elevator driven by a linear motor, called hereinafter a linear motor elevator or elevator, utilizes a linear motor as a driving means for elevating a cage for persons or articles and a counter weight alternatingly by means of a hoisting rope in a hoistway extending in a multistoried building.
In the linear motor elevator system, a reaction plate is secured in a suspended manner to an inner side wall of the hoistway and a stator is secured to the counter weight facing the reaction plate with space therebetween. The cage and the counter weight are alternatingly elevated up and down in the hoistway by a thrust force caused by passing electric current to the stator.
One example of the conventional linear motor elevator system of the type described above will be explained in detail hereunder with reference to FIGS. 6 to 8.
Referring to FIGS. 6 to 8, a hoistway for elevating the elevator system, including a cage 5 and a counter weight 7, is designated by reference numeral 1, and a frame 2 is horizontally stretched across the upper portion of the hoistway 1 and supported at both ends thereof to the side wall of the hoistway 1. A pair of deflector sheaves 3a and 3b are mounted to the frame 2 and a hoisting rope 4 is stretched around the sheaves 3a and 3b. The hoisting rope 4 has one end 4a on which is suspended the cage 5. Cage 5 is provided with a guide shoe 5a, to be elevated up and down along a guide rail 6 supported by the side wall of the hoistway 1. The hoisting rope 4 has the other end 4b by which is suspended the counter weight 7 provided with a guide shoe 7a to be elevated up and down along a guide rail 8 supported by the side wall of the hoistway 1 by means of a plurality of supporting members 12 through a plurality of anchor bolts 13 as shown in FIG. 7. A reaction plate 9 is supported in a suspended manner to the side wall of the hoistway 1 throughout substantially the entire vertical length of the side wall of the hoistway 1 by means of a plurality of brackets 10. A stator 11 is mounted to the counter weight 7 at a portion facing the reaction plate 9 with a slight gap C having a distance of several mm as shown in FIG. 7. The location and the adjustment of this gap C has a very significant meaning for the performance of the linear motor elevator system.
As shown in FIG. 7, the guide shoes 7a and the guide rails 8 for the counter weight 7 are disposed at vertically along both sides thereof.
The linear motor elevator system of the structure described above is elevated up and down by the thrust force caused by the electric current passing the stator 11. Namely, the cage 5 and the counter weight 7 both suspended by the hoisting rope 4 are elevated up and down alternatingly by this thrust force F shown in FIG. 8.
However, when the cage 5 and the counter weight 7 are elevated alternatingly, an attraction force k is caused between the reaction plate 9 and the stator 11. This attraction force k usually has a magnitude about 2 to 4 times that of the thrust force F. For example, when it is assumed that the usual thrust force F is of about 500 to 3000 kg, the attraction force k of about 1000 to 10,000 kg will be caused. Accordingly, as shown in a magnified manner in FIG. 8, the stator 11 and the reaction plate 9 are mutually attracted and, hence, the guide rails 8 are deformed or bent towards the reaction plate side by a reaction force of the guide shoe 7a of the counter weight 7 by a distance within a supporting distance of the supporting members 12. Therefore, it becomes impossible to maintain the prescribed distance of the gap C and in an adverse case, the elevating performance of the elevator system including suitable running speed, electric power consumption, stable arrival condition and the like may be damaged. In addition, the guide rails 8 and the reaction plate 9 are deformed, which may result in the loosening of the anchor bolts 13 of the supporting members 12 with time, to become dangerous. The use of an increased number of the anchor bolts 13 to obviate such defect may result in cost increases.